Isolation and identification of four new carboxylic acid metabolites of cortisol in man

Excretion of oxidated cortisol metabolites is markedly lower than previously assumed: An analysis of urinary cortoic acids in healthy children by GC-MS

Discovered about 50 years ago, the four C21 steroidal acids (α-)cortolic acid, β-cortolic acid, (α‑)cortolonic acid and β-cortolonic acid present the oxidative end products of cortisol metabolism. Undergoing renal elimination, these cortoic acids have been assumed to constitute up to 25 % of total urinary cortisol metabolites. However, their analysis has been difficult, only few data has been published in adults, and this class of steroids has become practically forgotten. Since data in children are lacking and nothing is known about their metabolism during human development, we aimed at establishing a more practical analytical method and determined their urinary concentrations in a high number of healthy subjects. In our method, 5-mL-aliquots of 24-hour urine samples were subjected to solid phase extraction (C18 cartridges), followed by strong anion exchange chromatography, and formation of 2-propylester-trimethylsilylether derivatives (2-PR/TMS). The cortoic acids were quantified by targeted gas chromatography-mass spectrometry (GC-MS) using a nonpolar GC column and selected ion monitoring (SIM). Baseline separation of all cortoic acids was achieved. Calibration graphs were linear (R2 > 0.98). Variations in precision and accuracy were less than 15 %, respectively. The detection limit was 100 pg (injected) with a signal-to-noise ratio of 3. 240 specimens from 24-hour urine collections from healthy children (120 boys, 120 girls, aged 3-18 years; DONALD study) were analyzed for cortoic acids and neutral cortisol metabolites to create first reference ranges. The profile of cortoic acids was dominated by α-cortolonic acid with excretion rates up to 70 µg/d. Absolute excretion rates of cortoic acids increased with age, their total excretion rates ranged between 11.0 and 127.3 µg/d (median 45.7 µg/d), but did not show any sexual dimorphism. Since cortoic acids make up only about 1 % of total urinary cortisol metabolites, determination of neutral urinary steroids reliably allows assessment of cortisol production. However, cortoic acids might present potential biomarkers of the body's redox state.

Human steroid biosynthesis, metabolism and excretion are differentially reflected by serum and urine steroid metabolomes: A comprehensive review

Advances in technology have allowed for the sensitive, specific, and simultaneous quantitative profiling of steroid precursors, bioactive steroids and inactive metabolites, facilitating comprehensive characterization of the serum and urine steroid metabolomes. The quantification of steroid panels is therefore gaining favor over quantification of single marker metabolites in the clinical and research laboratories. However, although the biochemical pathways for the biosynthesis and metabolism of steroid hormones are now well defined, a gulf still exists between this knowledge and its application to the measured steroid profiles. In this review, we present an overview of steroid hormone biosynthesis and metabolism by the liver and peripheral tissues, specifically highlighting the pathways linking and differentiating the serum and urine steroid metabolomes. A brief overview of the methodology used in steroid profiling is also provided.

The evolution of methods for urinary steroid metabolomics in clinical investigations particularly in childhood

The metabolites of cortisol, and the intermediates in the pathways from cholesterol to cortisol and the adrenal sex steroids can be analysed in a single separation of steroids by gas chromatography (GC) coupled to MS to give a urinary steroid profile (USP). Steroids individually and in profile are now commonly measured in plasma by liquid chromatography (LC) coupled with MS/MS. The steroid conjugates in urine can be determined after hydrolysis and derivative formation and for the first time without hydrolysis using GC-MS, GC-MS/MS and liquid chromatography with mass spectrometry (LC-MS/MS). The evolution of the technology, practicalities and clinical applications are examined in this review. The patterns and quantities of steroids changes through childhood. Information can be obtained on production rates, from which children with steroid excess and deficiency states can be recognised when presenting with obesity, adrenarche, adrenal suppression, hypertension, adrenal tumours, intersex condition and early puberty, as examples. Genetic defects in steroid production and action can be detected by abnormalities from the GC-MS of steroids in urine. New mechanisms of steroid synthesis and metabolism have been recognised through steroid profiling. GC with tandem mass spectrometry (GC-MS/MS) has been used for the tentative identification of unknown steroids in urine from newborn infants with congenital adrenal hyperplasia. Suggestions are made as to areas for future research and for future applications of steroid profiling. As routine hospital laboratories become more familiar with the problems of chromatographic and MS analysis they can consider steroid profiling in their test repertoire although with LC-MS/MS of urinary steroids this is unlikely to become a routine test because of the availability, cost and purity of the internal standards and the complexity of data interpretation. Steroid profiling with quantitative analysis by mass spectrometry (MS) after chromatography now provides the most versatile of tests of adrenal function in childhood.

Why do humans have two glucocorticoids: A question of intestinal fortitude

The main purpose of this review article is threefold (a) to try to address the question "why are two adrenal glucocorticoids, cortisol and corticosterone, secreted by humans and other mammalian species?", (b) to outline a hypothesis that under certain physiological conditions, corticosterone has additional biochemical functions over and above those of cortisol, and (c) to emphasize the role of gastrointestinal bacteria in chemically transforming corticosterone into metabolites and that these re-cycled metabolites can be reabsorbed from the enterohepatic circuit. Cortisol and its metabolites are not secreted into the bile and thus are excluded from the enterohepatic circuit. Corticosterone was the first steroid hormone isolated from adrenal gland extracts. Many believe that corticosterone functions identically to cortisol. Yet, corticosterone causes significant sodium retention and potassium secretion in Addisonian patients, unlike cortisol. In humans, corticosterone and its metabolite, 3α,5α-TH-corticosterone, are excreted via the bile in humans where they are transformed in the intestine by anaerobic bacteria into 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones. These metabolites inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase, being many-fold more potent than 3α,5α-TH-cortisol. Corticosterone has significantly lower Km's for both 11β-HSD2 and 11β-HSD1 enzymatic dehydrogenase activity, compared to cortisol. Patients diagnosed with 17α-hydroxylase deficiency have elevated blood pressure and high levels of circulating corticosterone, 3α,5α-TH-corticosterone, and their 21-dehydroxlated corticosterone derivatives. In humans, these 5α-corticosterone metabolites are likely to influence blood pressure regulation and Na(+) retention by inhibiting the rate of deactivation of cortisol by 11β-HSD isoforms.

Control of steroid 21-oic acid synthesis by peroxisome proliferator-activated receptor alpha and role of the hypothalamic-pituitary-adrenal axis

A previous study identified the peroxisome proliferator-activated receptor alpha (PPARalpha) activation biomarkers 21-steroid carboxylic acids 11beta-hydroxy-3,20-dioxopregn-4-en-21-oic acid (HDOPA) and 11beta,20-dihydroxy-3-oxo-pregn-4-en-21-oic acid (DHOPA). In the present study, the molecular mechanism and the metabolic pathway of their production were determined. The PPARalpha-specific time-dependent increases in HDOPA and 20alpha-DHOPA paralleled the development of adrenal cortex hyperplasia, hypercortisolism, and spleen atrophy, which was attenuated in adrenalectomized mice. Wy-14,643 activation of PPARalpha induced hepatic FGF21, which caused increased neuropeptide Y and agouti-related protein mRNAs in the hypothalamus, stimulation of the agouti-related protein/neuropeptide Y neurons, and activation of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in increased adrenal cortex hyperplasia and corticosterone production, revealing a link between PPARalpha and the HPA axis in controlling energy homeostasis and immune regulation. Corticosterone was demonstrated as the precursor of 21-carboxylic acids both in vivo and in vitro. Under PPARalpha activation, the classic reductive metabolic pathway of corticosterone was suppressed, whereas an alternative oxidative pathway was uncovered that leads to the sequential oxidation on carbon 21 resulting in HDOPA. The latter was then reduced to the end product 20alpha-DHOPA. Hepatic cytochromes P450, aldehyde dehydrogenase (ALDH3A2), and 21-hydroxysteroid dehydrogenase (AKR1C18) were found to be involved in this pathway. Activation of PPARalpha resulted in the induction of Aldh3a2 and Akr1c18, both of which were confirmed as target genes through introduction of promoter luciferase reporter constructs into mouse livers in vivo. This study underscores the power of mass spectrometry-based metabolomics combined with genomic and physiologic analyses in identifying downstream metabolic biomarkers and the corresponding upstream molecular mechanisms.

Corticosteroid side-chain oxidations--I. Structural effects on the excreted isotope ratios of 4-14C- and 21-3H-labelled corticosteroid metabolites in rabbit urine

The metabolic fates of 4-14C- and 21-3H-labelled corticosteroids have been investigated in the rabbit by analysis of the normalized isotope ratios of neutral and acidic metabolites excreted in the urine. Isotope ratios of excreted radioactivity declined in the order cortisol (F) greater than corticosterone (B) greater than 11-desoxycortisol (S) greater than deoxycorticosterone (DOC). Steroid acids, isolated in alumina fraction C, represented 19.0, 15.0, 9.7 and 2.7% of the doses of DOC, B, S and F, respectively, and the isotope ratios declined in the order F greater than B greater than S greater than DOC. HPLC of steroid acid methyl ester derivatives indicated generally low isotope ratios for DOC and S steroid acids, consistent with complete side-chain oxidation to 20-oxo-21-oic acids and/or 17-carboxylic acids. Several B metabolite methyl esters peaks also exhibited low isotope ratios, but both B and F metabolites gave methyl esters that retained significant tritium consistent with the presence of 20-hydroxysteroid acids. The 21-hydroxy-steroid metabolite fractions had isotope ratios of F = S greater than B greater than DOC. HPLC showed that 20-oxo (tetrahydro) metabolites of B and F had reduced isotope ratios unlike the C-20 reduced (hexahydro) metabolites of DOC and S. It may be concluded that the metabolic fate of the corticoid side-chain in the rabbit is dependent on the steroid structure and may result in the excretion of both 20-oxo and 20-hydroxysteroid acids.

High-performance liquid chromatographic determination of cortolic and cortolonic acids as pyrenyl ester derivatives

A new procedure is described for the detection of the acidic metabolites of cortisol (cortoic acids) as the pyrenylmethyl-21-oic esters. The derivatizing reagent, diazomethylpyrene, was prepared by an improved procedure. The reagent was used at room temperature, required no catalyst, and was not restricted by stoichiometric requirements. The steroid esters were separated by reversed-phase high-performance liquid chromatography and analyzed simultaneously by their ultraviolet absorbance and fluorescence characteristics. Identities of the products were confirmed using the photodiode array detector to determine spectral profiles, absorbance maxima, and absorbance ratios. Further confirmation of identity of the cortoic acid esters used mass spectrometry under normal and collision-activated dissociation conditions. With the method described, a linear spectral response was obtained between 8 and 1680 fmol. Application of the technique to the analysis of steroid acids in human urine indicated the presence of cortoic acids.

Corticosteroid side-chain isomerase in mouse organs: kinetic and immunologic studies

We have investigated the distribution of corticosteroid side-chain (CSC) isomerase in the tissues of mice using as criteria its enzyme activity and immunoreactivity with monospecific polyclonal antibodies generated in rabbits. CSC isomerase was present in all organs examined. The liver and kidney contained the highest activity. The strain-dependent differences that we had previously reported for liver (i.e., BALB/c greater than C57BL/6) extended to the other organs, including the kidney, brain, heart, muscle, pancreas, testis, thymus, and lung. Western blot analysis showed a single antigen, identical in all tissues, corresponding in mobility to purified CSC isomerase. The intensities of the bands were generally proportional to enzyme activities. Titration of homogeneous enzyme with the IgG fraction of antiserum (unfractionated serum had some CSC isomerase activity) caused an increase in activity, followed by rapid inactivation after the addition of more antiserum. The broad distribution of CSC isomerase suggests that the ketol-aldol interconversion of the CSC may play a role other than, or in addition to, initiating metabolic inactivation of corticosteroids.

Detailed study of oxidative esterification and elimination reactions undergone by a steroidal 17 alpha-benzoyloxy-20-oxo-21-aldehyde

The reaction of 17 alpha-benzoyloxy-11 beta-hydroxy-3,20-dioxo-1, 4-pregnadien-21-al as the hemiacetal (1) with methanol:acetic acid:potassium cyanide:manganese dioxide followed by acetylation and preparative HPLC of the reaction mixture afforded 11 crystalline products. These products can be conveniently divided into three categories representing side-chain cleavage and oxidative esterification with or without elimination of the benzoyloxy group. Of special interest was the stereospecific formation of the C-17 cyanohydrin acetate 4a and the cis delta 17(20) enol acetate methyl ester 5. On the other hand, nonstereospecific addition of HCN to the side chain gave the C-20 epimeric cyanohydrin acetates 7a and 7b. The use of activated versus nonactivated MnO2 plays a major role in determining the quantitative distribution of the products. It was also discovered that even in the absence of MnO2, the reaction goes to completion. A proposed mechanism which explains the formation of all products is presented.

Purification and characterization of corticosteroid side chain isomerase

Corticosteroid side chain isomerase of rat liver catalyzes the interconversion of the ketol (20-oxo-21-ol) and aldol (20-hydroxy-21-al) forms of the corticosteroid side chain. The enzyme has now been purified to apparent homogeneity from rat liver cytosol by sequential chromatography on anionic, hydroxylapatite, and gel filtration columns. Ketol-aldol isomerization is followed by measuring the exchange of tritium from 21-tritiated steroids with water. The native enzyme is a dimer of MW 44,000. The isoelectric point is 4.8 +/- 0.1 pH units. The purified enzyme is stimulated by Co3+ or Ni2+. The enzyme utilizes 11-deoxycorticosterone, corticosterone, and 17-deoxycortisol as substrate but not cortisol, tetrahydrocortisol, and prednisolone. Tritium-water exchange of (21S)-[21-3H]DOC is a pseudo-first-order reaction; 21-3H exchange from the 21R isomer proceeds with first-order kinetics only after a lag associated with its epimerization to the 21S form.

Synthesis of tritium labeled cortoic acids

A procedure is described for the microsynthesis and purification of the high specific activity tritium labeled cortisol metabolites, 20 alpha- and 20 beta-cortolic acids and 20 alpha- and 20 beta-cortolonic acids.

Constituents of human meconium--III. Identification of 3,20-dihydroxypregnan-21-oic acids

Seven 3,20-dihydroxypregnan-21-oic acids (C21) were detected by capillary gas chromatography-mass spectrometry in the acid fraction isolated from human meconium after solvolysis and mild alkaline hydrolysis. The two major acids were isolated and identified by nmr as 3 alpha, 20 alpha-dihydroxy-5 alpha-and 3 alpha, 20 alpha-dihydroxy-5 beta-pregnan-21-oic acids. Two minor C21 components were identified as 3 alpha, 20 beta-dihydroxy-5 beta-pregnan-21-oic and 3 beta, 20 alpha-dihydroxypregn-5-en-21-oic acids. A trace amount of 3 alpha, 20 beta-dihydroxy-5 alpha-, 3 beta, 20 alpha-dihydroxy-5 alpha-pregnan-21-oic, and 3 beta, 20 beta-dihydroxypregn-5-en-21-oic acids were also detected. The identification of these C21 acids was confirmed by mass spectral and chromatographic comparison with standards of eight saturated and two 5-unsaturated 3, 20-dihydroxylated C21 acids. The decisive predominance of 20 alpha isomers confirmed the native presence of C21 acids in meconium. Six acids, with an exception of 3 beta, 20 beta-dihydroxy-pregn-5-en-21-oic acid, were detected in the extract of meconium prepared in the presence of large excess of sodium borohydride; this minor acid, together with a part of its 20-epimer, was evidently formed as result of the artefactual oxidation of 21-hydroxypregnenolone, the known constituent of meconium. The co-occurrence of relatively high concentrations of C21 acids and monohydroxylated C20 acids, previously detected in human meconium, pointed to the significance of the oxidative catabolism of neutral C21 steroids in the case of feto-placental-maternal unit.

Acidic metabolites. VI. 20 alpha-isosteroids as intermediates in 20 alpha-dihydrosteroid formation

We have previously shown that human subjects metabolize the 20 beta-epimer of isocortisol (11 beta, 17,20 beta-trihydroxy-3-oxo-pregn-4-en-21-al) to both 20 alpha- and 20 beta-hydroxy steroid end products. In this paper we describe the synthesis of tritium labeled 20 alpha-epimers of isocortisol and isoTHF (3 alpha, 11 beta, 17,20 alpha-tetrahydroxy-5 beta-pregnan-21-al) and their metabolic fate in humans. Both steroids yielded 20 alpha-hydroxy urinary neutral end-products (cortols and cortolones) and no 20 beta-hydroxy epimers. Regeneration of 17-ketols from aldols occurred to a small extent with isoTHF, but not with isocortisol. Isocortisol and isoTHF yielded less cortoic acids than did the corresponding ketols. The results provide further evidence that in man the stereochemistry at C-20 of the end-products of corticosteroid metabolism is determined by the configuration of the aldol at C-20 prior to subsequent metabolic events.

Influence of thyroid function on the in vivo cortisol in equilibrium cortisone equilibrium in man

To evaluate the effect of thyroid function on the in vivo cortisol in equilibrium cortisone (F in equilibrium E) equilibrium, double-labeled cortisol tracer techniques were used to measure separately the rates of the F leads to E and E leads to F reactions in 4 euthyroid, 2 hypothyroid, and 2 hyperthyroid subjects. The rate of the F leads to E reaction was calculated from the appearance rate of 3H in body water after the i.v. injection of [11 alpha-3H]-cortisol; the rate of the E leads to F reaction was calculated from the difference in the plasma turn-over rates of [11 alpha-3H]-cortisol, and [4-14C]-cortisol after simultaneous i.v. injection of both tracers; the F in equilibrium E set-point was calculated by dividing the F leads to E rate by the E leads to F rate. In euthyroid subjects the F leads to E reaction rate averaged 1.6%/min, the E leads to F reaction rate averaged 1.0%/min, and the F in equilibrium E set-point averaged 1.6. In hyperthyroid subjects the two reaction rates were supranormal: the F leads to E rate averaged greater than or equal to 3.9%/min and the E leads to F rate averaged 1.54%/min; since the increase in the F leads to E rate was proportionally greater, the F in equilibrium E set-point (average greater than or equal to 2.6) was displaced towards cortisone. In hypothyroid subjects both reaction rates were equally slowed, to an average of 1.0%/min (F leads to E) and 0.68%/min (E leads to F); the F in equilibrium E set-point averaged 1.65, the same as in euthyroid subjects. Displacement of the F in equilibrium E equilibrium towards cortisone in hyperthyroid subjects appears to account for their elevated urinary THE/THF ratios, but the normal F in equilibrium E set-point in hypothyroid subjects makes it necessary to invoke a different mechanism for their depressed THE/THF ratio; it is suggested that increased conversion of THE to cortoic acids may be the responsible factor.

Aldose and aldehyde reductase exhibit isocorticosteroid reductase activity

In this paper we describe the reduction of corticosteroid metabolites containing the 17 beta-aldol side chain (isocorticosteroids) by aldose and aldehyde reductase from human tissues. Aldose reductase catalyzed the reduction of the aldehydes derived from cortisol and corticosterone at about the same rate, whereas aldehyde reductase preferentially acted on the aldehydes derived from 17-deoxycorticosteroids. At comparable rates of reduction the Michaelis constants for the best steroid aldehydes were one order of magnitude lower than for the hitherto best substrates. We propose that aldose and aldehyde reductase participate in the conversion of the corticosteroid ketol side chain to the glycol side chain via an aldol intermediate by the 'long loop' pathway proposed by Monder and Bradlow [(1977) J. Steroid Biochem. 8, 897-908].

Constituents of human meconium--I. Identification of 3-hydroxy-etianic acids

The monohydroxylated fraction of bile acids of human meconium was analyzed by capillary GC-MS. In the sulfate-glucuronide fraction three saturated, and one unsaturated C20 steroidal acids were found. These acids were identified as 3 alpha-hydroxy-5 alpha-, 3 alpha-hydroxy-5 beta-,3 beta-hydroxy-5 alpha-androstane-17 beta-carboxylic, and 3 beta-hydroxyandrost-5-ene-17 beta-carboxylic based on the unequivocal GC-MS comparison with standards of all possible epimers at C-3, 5 and 17. The amount of the major C20 acid, 3 alpha-hydroxy-5 alpha-androstane-17 beta-carboxylic, in meconium was 0.2 nmol/g, i.e. 5 to 10 times the amount of lithocholic acid. To prevent the oxidation of 21-hydroxy-20-oxopregnanes to C20 acids meconium was extracted in the presence of sodium borohydride. In the absence of this reducing agent the amount of 3 beta-hydroxyandrost-5-ene-17 beta-carboxylic acid was increased and its 17 alpha-epimer could be detected. This indicates partial artifactual formation of this C20 acid from 21-hydroxypregnenolone, which is known to be present in human meconium. The amount of the saturated C20 acids was unaffected by the presence of sodium borohydride in the extraction medium, and their native occurence in human meconium was further confirmed by the absence of their 17 alpha-epimers in extracts obtained both with and without borohydride. The probable metabolic origin of C20 acids in the fetal-placental-maternal unit is discussed.

Degradation of hydrocortisone in a zinc oxide lotion

An extemporaneous topical steroid formulation, prepared from a zinc oxide lotion and hydrocortisone lotion BPC, had poor stability. Hydrocortisone decomposed mainly to the 21-aldehyde, but other degradation products were also identified by HPLC. The decomposition process could be described by first-order kinetics. Stabilization methods employing pH adjustment, antioxidants and chelating agents were unsuccessful. The study emphasizes the dangers of diluting commercial formulations with unrecommended bases and indicates the modes of decomposition of hydrocortisone in a formulation.

Oxidation of corticosteroids to steroidal 20-hydroxy-21-oic acids by mouse liver

We have studied the enzyme catalyzed oxidation of 11-deoxycorticosterone to 20-hydroxy-3-oxo-4-pregnen-21-oic acid (pregnolic acid) in mouse liver. Enzyme activity, though variable, was higher than that of other species. Pregnolic acid was identified as the free acid, as the methyl ester by thin layer chromatography, and as the p-bromophenacyl ester by high performance liquid chromatography. With [4-14C, 21-3H]-DOC as substrate, exchange of tritium with water (interpreted as due to the reversible isomerization of the ketol to aldol form by the side chain) and the overall conversion of the ketol side chain to hydroxy acid was catalyzed by the post-microsomal supernatant fraction. Although we could not physically separate tritium exchange and acid production, pregnolic acid formation could be decreased or eliminated while tritium exchange was retained, consistent with our previous conclusion that isomerization to aldol was a precondition for acid formation. In preparations that made no acid, [4-14C]-DOC was recovered, depleted of tritium. The rate of exchange of [21S, 21-3H]-DOC with water was faster than [21R, 21-3H]-DOC. The stereochemistry of pregnolic acid at C-20 was 85-90% R (i.e.. 20 alpha-hydroxy-21-oic acid). The Km for isomerase with [21RS-21(3) H-DOC was 4.3 x 10(-5); Km for pregnolic acid formation was 8.0 x 10(-5) M. Corticosterone was oxidized to acid metabolites at 20% the rate of DOC.

Oxidation of the 17-aldol (20 beta hydroxy-21-aldehyde) intermediate of corticosteroid metabolism to hydroxy acids by homogeneous human liver aldehyde dehydrogenases

In human liver, the oxidation of corticosteroids to 20-hydroxy-21-oic acids proceeds via the formation and oxidation of aldol (20-hydroxy-21-aldehyde) intermediates. Human liver aldehyde dehydrogenases E1 and E2, which we have previously purified to homogeneity, catalyzed the oxidation of the aldol isomer of cortisol (isocortisol) or of 11-deoxycorticosterone (isoDOC) by E1 and E2 respectively, were identified by the criteria of chromatographic mobility, derivatization, and reverse isotope dilution of 4-14C labeled acid end products. Both enzymes showed broad substrate specificity and oxidized both 17-hydroxy and 17-deoxy steroids, though at widely varying rates. Kinetic analysis of the course of oxidation of isocortisol and isoDOC by NAD+ gave intersecting initial velocity plots that conform with a sequential mechanism. The inhibition patterns for both enzymes with thionicotinamide adenine dinucleotide or chloral hydrate were consistent with random sequential behavior.

Oxidation of cortisol to hydroxy acid metabolites by liver cytosol

Cytosols (post-microsomal supernatants) prepared from rat, hamster and mouse livers oxidized cortisol to 11 beta, 17, 20-trihydroxy-3-oxo-pregn-4-en-21-oic acids. Mouse liver enzymes yielded over 90% 20 alpha-hydroxy epimer from cortisol, 21-dehydrocortisol (11 alpha, 17-dihydroxy-3,20-dioxo-pregn-4-en-21-aldehyde), and 20 alpha-isocortisol (11 alpha, 17, 20 alpha-trihydroxy-3-oxo-pregn-4-en-21-aldehyde). The 20 beta-epimer of isocortisol yielded both 20 alpha- and 20 beta-hydroxy acid. Rat and hamster liver cytosols converted, 21-dehydrocortisol and 20 alpha-isocortisol to both 20 alpha and 20 beta-hydroxy acids, with the former predominant. The hamster enzyme oxidized 20 beta-isocortisol mainly to the 20 beta-hydroxy acid. The results support our conclusion that both 17 alpha-hydroxy and 17-deoxy corticosteroids are oxidized to hydroxy acids by similar pathways and that isosteroids are obligatory intermediates.

Constituents of human meconium: II. Identification of steroidal acids with 21 and 22 carbon atoms

Monohydroxylated acid fraction isolated from human meconium was found to contain, in addition to C20 and C24 acids identified previously, three C22 bile acids-(20S)-3 alpha-hydroxy-23,24-bisnor-5 beta-cholan-22-oic, (20S)- and (20R)-3 beta-hydroxy-23,24-bisnor-chol-5-en-22-oic, and one C21 acid-3 beta-hydroxypregn-5-en-21-oic. These compounds were identified by capillary gas chromatography-mass spectrometry and by comparison with standards. It is postulated that these C22 acids, as well as the two monohydroxylated C24 bile acids (lithocholic and 3 beta-hydroxychol-5-enoic) are produced in the maternal intestine by microbial flora and transferred to the fetus through the placenta.

Gas chromatographic and mass spectrometric analysis of urinary acidic metabolites of cortisol

A method is described suitable for the analysis of the urinary acidic metabolites of cortisol which are amongst the major metabolites of this hormone (5-25% of secretion). Following hydrolysis of the urinary glucuronide conjugates and extraction of the freed steroids, methyl ester-trimethylsilyl ethers were prepared for gas chromatographic analysis. This analysis was carried out on open tubular columns coated with Carbowax stationary phase. The polar phase column permitted the complete resolution of the four acidic metabolites: alpha-cortolonic, beta-cortolonic, alpha-cortolic and beta-cortolic acids.

Structure-activity relationships in glucocorticoids

Meaningful answers to the question of the relationship between glucocorticoid structure and activity have emerged. Structural change has predictable effects on susceptibility to the action of metabolizing enzymes, on receptor affinity, and on intrinsic activity. These effects are, in principle, amenable to mathematical modeling techniques. The fascinating possibility of being able to calculate receptor affinity directly from chemical structure has already been realized through the development of an equation [19] that allows the calculation of receptor binding of any glucocorticoid from structural parameters. Utilizing knowledge of the free energy contributions of the substituents and the hydrophobicity and A-ring conformation of the steroids, receptor affinity for a large number of compounds could be described in terms of four parameters. A general relationship was derived relating the equilibrium dissociation constant to a surface area term, a polar interaction term, and A-ring tilt term, and a size limitation function for the 9 alpha-substituent. The excellent correlation obtained suggests that these four factors are the major determinants of glucocorticoid receptor interactions. It is clear that the use of a mathematical relationship that defines the strength of steroid-receptor interaction is a valuable tool for investigating structure-activity relationships. This would be especially true in the design of steroid drugs. The use of a linear free-energy equation is superior to the assumption of substituent additivity in predicting binding affinities. This type of relationship will be useful in the preparation of steroids for use in affinity labeling studies and should be adaptable to other binding systems in which it is desirable to obtain synthetic analogs for more potent activity or specificity.

Acidic metabolite of prednisolone

The metabolic fate of the 17beta-ketol side chain of (21-3H) prednisolone was studied with an enzyme preparation from male golden hamster liver. The acidic metabolite of prednisolone was identified by mass spectrometry as 11beta, 17alpha,20epsilon-trihydroxy-3-oxo-1,4-pregnadien-21-oic acid. The enzyme showed substrate specificity, depending on the nature of substituent on the steroid nucleus.

Effect of structure on the excretion of steroidal acids in human urine and their potential colorimetric assay as 17-oxogenic steroids

Following the oral administration of tritiated coricosterone, cortisol, deoxycorticosterone and progesterone to human subjects, 14.9%, 12.8%, 3.4% and 2.1% of the dose was recovered in the acidic metabolite fraction of 48 h urines after conventional hydrolysis and solvent partition. Neutral and acidic 17-oxogenic steroids (17-OGS) excreted in 24 h urines were also measured with the Zimmermann color reaction. The acidic 17-IGS accounted for 14.1%, 16.4% and 12.1% of the fractionated 17-OGS in the urines of normal and pregnant females and normal males respectively. From structural considerations, it was concluded that only 17-hydroxylated steroidal acids, with a 20-hydroxy-21-oic acid side chain and derived predominantly from cortisol, would be estimated as 17-OGS after oxidation with sodium periodate. 17-Dexy steroidal acids resemble the neutral 17-deoxycorticosteroids in undergoing side chain oxication to 17-aldehydes which do not form Zimmermann chromogens. The excretion of both neutral and acidic 17-OGS was suppressible with dexamethasone administration.